1. Field of the Invention
This invention relates to an apparatus for scraping the inside diameters of well casings.
2. Description of the Prior Art
In the drilling completion or workover of an oil well, the interior of the well casing or other conduit, is exposed to a variety of materials which tend to adhere to the internal surface of the conduit, such as drilling mud, cements, rust and scale. To permit the unimpeded passage of pumping equipment, perforating equipment and the like into and out of the well casing, it is obviously desirable that all foreign substances adhering to the interior walls of the casing first be removed. Additionally, burrs resulting from perforation operations prohibit the free passage of packing and other elements through the well, and such burrs of necessity must therefore be removed.
To effect such removal, a number of scraping tools have heretofore been proposed. Such prior art scrapers have been characterized in having only a limited effective diametrical range of operation. For example, it is known that a seven inch exterior diameter well casing may have five or more different internal diameters, dependent on the casing weight required for the particular installation. As a result, the scraping apparatus heretofore available required the installation of at least three different sizes of blade blocks, one at a time, on the tool support in order to scrape the full range of internal diameters provided in seven inch casing. Furthermore, prior art scraping mechanisms were not susceptible to ready adjustment of the effective working diameter of the scraping tools, requiring that the tool be practically disassembled in order to achieve any adjustment.
Similarily, prior art scraping apparatuses did not incorporate any means for compensating for wear on the blade blocks, requiring the replacement of the entire blade block assembly whenever any significant wear was achieved. Additionally, the mounting of blade blocks on conventional apparatus was such that if a jam occurred between the teeth of the blade block and an obstruction in the casing, it was generally quite difficult to pull the tool free.
It is therefore apparent that there is a distinct need for an improved, more flexible, readily adjustable scraping apparatus for well casings.